Mikuni float bowl rubber bungs

[Dennis menace]

I have bought a new pair of Mikuni BST38 carbs on fleabay. The float bowls each have two rubber bungs as blanking plugs and I want to know if these are supposed to be replaced with more substantial threaded plugs? I am worried the rubber bungs will leak air or petrol as they just push in. The holes in which they fit are about 10mm diameter with a fine metric thread. An hydraulic banjo bolt fits the hole.

A Ducat suite article shows the bungs about halfway down the article:

http://www.ducatisuite.com/carbsynch.html

The original carbs have no blanking plugs.

Many thanks.

[Unit 18]

If it's the ones from this picture they are covering the threads for the carb heating system and can be left there.

http://www.ducatisuite.com/images/carbadjust2link.jpg

[Dennis menace]

Great, many thanks.
:hail: